Perhaps you should try some spelling variations:
"modified notion approximation algorithms" » "modified network approximation algorithms", "modified time approximation algorithms", "modified one approximation algorithms"
"modified model selection algorithm" » "modified model solution algorithm", "modified model estimation algorithm", "modified model reduction algorithm", "modified market selection algorithm", "modified male selection algorithm"

You may be able to get more results by adjusting your search query.

• Performing a fuzzy search may retrieve terms with similar spellings: (("modified notion approximation algorithms") or ("modified model selection algorithm"))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (("modified notion approximation algorithms") OR ("modified model selection algorithm")).
• Removing quotes may allow a broader search: (( modified notion approximation algorithms ) or ( modified model selection algorithm )).
• Adding a wildcard symbol may retrieve word variants: (("modified notion approximation algorithms") or ("modified model selection algorithm"))*.